1. Field of the Invention
The present invention relates to a method and to a machine for the manufacture of a fiber web, and, more particularly, to the manufacture of a tissue web or of a hygienic web.
2. Description of the Related Art
The use of so-called throughflow apparatuses or TAD drying apparatuses (TAD=through air drying) in paper making machines is known (see for example WO 97/03247, U.S. Pat. No. 4,036,684). The TAD units have previously made up a large part of the total costs of the respective paper making machines. The energy requirements for a TAD machine with a dual wire former is very high and, in particular, much higher than, for example, those for a crescent former. For example, approximately 12 vacuum pumps have thus been required up to now in one TAD machine in order to achieve the desired dry content and degree of cleansing.
In a conventional TAD machine with, for example, a dual wire former, the web must be transferred from the forming zone to the TAD zone, with the desired dry content being able to lie on the web transfer, for example, in a range from approximately 22 to approximately 26.5%, depending on the basis weight. The web is then guided with this dry content, for example, to a wet suction box effecting a wet imprinting (wet molding) and then to the TAD drum. The named dry content has previously only been achieved, however, with a relatively high energy effort.
What is needed in the art is an improved method and an improved machine with which an optimum quality of the respective final product can be achieved with an energy effort which is as low as possible. In particular the energy effort required in connection with the vacuum generation in the dewatering of the fiber web should be reduced in this process.